Yu-Gi-Oh! Monster Capsule GB is a video game for the Game Boy Color. It has only been released in Japan. The game uses a modified version of Monster World.

Seto Kaiba possesses the Millennium Ring and is captured by its power while his mind was shattered after losing to Dark Yugi at "Death-T". Kaiba then invites Yugi Muto and all of Yugi's friends to "Duel Tower". Once in the tower, the ring uses its power to transfer the souls of Katsuya Jonouchi, Anzu Mazaki, Hiroto Honda, Ryo Bakura, and Sugoroku Mutou. In order to get his friends and grandfather back, Yugi has to defeat Kaiba and his minions in the "Monster World Tournament" using "Monster Capsules" (MC).